An “Unknown” status occurs when a valid response is not received from your payment gateway.
When a donor clicks to process a donation, their payment information is sent through a secure channel to your payment gateway, to either approve or decline the transaction with the donor's bank. All of this happens practically instantly.
In very rare circumstances, we never hear back regarding the status of the donation or the gateway's response takes too long. This might be due to a delay with card processor, a connection issue, or a held payment.
Because your donor cannot wait forever for a response from your gateway, we let them know that their payment is "pending" and to return in 10-15 minutes if they do not receive an email thanking them for their gift (or a tax receipt). On the back-end, though, we mark the transaction as "Unknown" - essentially meaning that the gateway never responded and therefore, we cannot accurately determine if it was successful or declined. Unknown transactions can be found only in the Transactions Report of your event.
You might later see the donation show up in your payment account if the transaction was successful. If so, let your Client Experience Manager know so that we can accurately credit the donor for their contribution.